What makes neurons excitable cells?

The outer surface of the axonal membrane possesses a positive charge while its inner surface becomes negatively charged and therefore is polarised The sodium-potassium pump transports 3 Na⁺ ions outwards for 2 K⁺ ions into the cell.When a neuron is resting, the axonal membrane is more permeable to potassium ions (K⁺) and nearly impermeable to sodium ions (Na⁺). The axoplasm inside the axon contains high concentration of K⁺ and low concentration of Na⁺. The resting potential of the plasma membrane of a neuron is the electrical potential difference across the resting plasma membrane when the membrane is in a polarised state